Electron cooling is a central technology to the invention proposed herein. Electron cooling was originally proposed by Budker in 1966. The basis for his proposal came from work done by Spitzer (1956) who showed that warm ions come to equilibrium with cooler electrons in a plasma. Due to the much larger mass of the ion, the final rms speed of the ions is much less than that of the electrons. Budker realized that an electron beam is simply a moving electron plasma. By superimposing an ion beam on a co-moving electron beam, warmer ions are cooled by the electron beam.
In the 1970's electron cooling was demonstrated to be an extremely good way of increasing the phase space density and stored lifetime of proton beams. Cooling times of between one and ten seconds were reported by experiments at Novosibirsk, CERN, and Fermilab. An experiment completed in Middleton, Wis. culminated in the construction of an electron cooler capable of cooling intermediate energy (about 5 GeV) antiproton beams.
Uses of high intensity, low energy ion beams may include the generation of photons, neutrons and a variety of nuclear isotopes, with improved efficiency and yield. Neutrons, isotopes, or photons are used in numerous applications. Neutron applications include boron neutron capture therapy, neutron radiography, and particularly, neutron irradiation for explosive detection, contraband detection, corrosion detection, and other types of non-destructive analysis. Isotope applications include positron emission tomography (PET). Photon (or gamma ray) applications include photonuclear interrogation which has been proposed as another means of detecting contraband and explosives. Photonuclear interrogation is also used for medical imaging and other nondestructive analysis of a wide range of materials.
Uses of high intensity, low energy ion beams may also include the production of energy through fusion interactions. Several nuclear reactions are known to produce much more energy than the energy required to initiate the interaction, and the initiation energy is very low by particle beam standards.
Conventional techniques in electron cooling use an electron beam and superimpose that electron beam onto the ion beam. Particle collisions between the two beams result in ion beam imperfections being transferred to the electron beam. The electron beam is then separated from the ion beam, and the electron beam is then collected in a collection device. Conventional techniques involve a direct acceleration of the electron beam from its source at a cathode, using electrodes biased positively with respect to the cathode and arranged so as to accelerate the electrons so that they have the same velocity as the ions. Typically, solenoidal and torroidal magnetic fields are used to guide the electron beam onto the ion beam, and then into the collection device. However, the conventional technique has serious difficulty for low energy situations. Conventional electron beams have an intensity that is limited by the electron beam's self space charge, and this limit is severe for low energy electron beams.
Accordingly, there is a need for an improved method and system for generating electron beams that will overcome the intensity limit of conventional techniques.